The Finding

The tail rotor control system was first inspected at the crash site. This identified that the
input lever mechanism was not attached to the control shaft. The pin, spacers and one
of the locating bearings were missing from the lever. The locking nut and pin carrier were
found loose in the tail rotor fairing and were bonded together (they should be separate
components). The threads of the nut appeared to be undamaged. There was no evidence
of the split pin, and the control shaft threaded section had moved inside the outer shaft and
was no longer visible. The control shaft, the locking nut and pin carrier, and the duplex bearing/sliding unit
assembly were removed from the wreckage and inspected in detail. The locking nut on the
bearing end of the control shaft was found to have a torque load significantly higher than
the required assembly value. The inner races of the bearing could only be rotated a few
degrees in either direction by hand. There was a build-up of black grease inside the slider
unit around the inboard face of the duplex bearing. The section of the control shaft adjacent
to this bearing face showed evidence of burnt-on grease and was discoloured along its
length
The evidence gathered to date shows that the loss of control of the helicopter resulted
from the tail rotor actuator control shaft becoming disconnected from the actuator lever
mechanism. Disconnection of the control shaft from the lever prevented the feedback
mechanism for the tail rotor actuator from operating and the tail rotor actuator from
responding to yaw control inputs. Loss of the feedback mechanism rendered the yaw
stops ineffective, allowing the tail rotor actuator to continue changing the pitch of the
tail rotor blades until they reached the physical limit of their travel. This resulted in an
uncontrollable right yaw.

LONG STORY SHORT

A pin was broken and was not on the tail rotor which allows the pilot to manipulate the tail rotor.